In recent years, a technology relating to millimeter waves has been developed, and has been used in wide fields such as an in-vehicle radar, wireless communication, biological information sensing, and the like, for example. When the millimeter wave is used, since a high-gain antenna having high straightness and directionality can be designed and a wavelength is short, merits such as miniaturization of a device are obtained. However, an unintended signal component referred to as spurious (unwanted emission) is also emitted, so that it may influence signal characteristics of a radar apparatus. Patent Document 1 discloses an example of the related art relating to absorption of the spurious (unwanted emission).
A radio wave absorber of the related art disclosed in Patent Document 1 includes a magnetic layer including a magnetic material having a micro structure in which particle diameters are controlled to 1 to 100 nm. Thereby, the radio wave absorber has a thin shape having a thickness of 1 mm or less, and has also favorable absorption performance for an electromagnetic wave of high frequency.
Patent Document 1: JP-A-2002-158484
However, the related art disclosed in Patent Document 1 has a problem that it is necessary to provide a separate member such as the radio wave absorber when absorbing the spurious, although the member is thin. Accordingly, it is concerned that it is not possible to miniaturize a device configured to use the millimeter wave.